[Qgis-user] hillshade render style
Andreas Plesch
andreasplesch at netscape.net
Sat Apr 8 08:27:11 PDT 2017
I could not find documentation on the hillshade render type style. While it
is rather self-explanatory, the multidirectional option could benefit from
explanation. I am looking at the source here:
http://qgis.org/api/2.18/qgshillshaderenderer_8cpp_source.html
and it points to
http://pubs.usgs.gov/of/1992/of92-422/of92-422.pdf
which uses a weighted average of hillshadings from four fixed directions.
The weight is squared sine of the difference between the aspect and each
illumination azimuth, emphasizing the darker slopes. The qgis code seems to
modify that a bit by making the four directions relative to the user
defined azimuth.
Is this a correct understanding ?
I am thinking about simulating this with webgl based (Phong) shading by
four directional lights.
-Andreas
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